Display screen or portion thereof with transitional graphical user interface



FIG. 1 is a front view of a display screen or portion thereof with transitional graphical user interface showing the first image in a sequence.

FIG. 2 is the second image thereof.

FIG. 3 is the third image thereof.

FIG. 4 is the fourth image thereof; and,

FIG. 5 is the fifth image thereof.

The appearance of the transitional image sequentially transitions between the images shown in FIGS. 1-5. The process or period in which one image transitions to another image forms no part of the claimed design.

The outermost broken line rectangle in each figure illustrates a display screen or portion thereof and forms no part of the claimed design. The remaining broken lines in the drawings, including all text shown and the Capital-Dome-icon, illustrate portions of the graphical user interface that form no part of the claimed design. 

CLAIM The ornamental design for a display screen or portion thereof with transitional graphical user interface, as shown and described. 